Chen theorises that its because Apple needs to rush hardware to market, so instead of properly testing their firmware - which shouldn't be that hard, it's a frakking keyboard - they just make the firmware flashable instead. This is indeed what happened when the keyboard first came out.

What we need to know is this: how hard is it to achieve this on keyboards from other manufacturers?

What we need to know is this: how hard is it to achieve this on keyboards from other manufacturers?

Even if it were possible (and I suspect this is going to turn out to be Apple specific) the exploit would surely need to be customized for the keyboard family. And for the platform.

Apple would still be the logical target because MacOSX and Apple keyboards go together like... oh... "War" and "Pestilence". If the exploit code will run, you can be reasonably certain that the keyboard is going to be Apple, and thus vulnerable, most of the time.

Note that this reasoning applies to any future hardware-based exploits, and not just to keyboards.